Logical Reasoning

Coding and Decoding-Coding-Decoding

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Coding - Decoding Aptitude basics, practice questions, answers and explanations 
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Coding is a method of transmitting a message between the sender and the receiver that no third person can understand it. The coding and decoding one’s ability of deciphering the rule and breaking the code to decipher the message will be tested to know.


1) Observe alphabets or numbers given in the code keenly.

2) Find the sequence it follows whether it is ascending or descending.

3) Detect the rule in which the alphabets/numbers/words follow.

4) Fill the appropriate letter/number/word in the blank given.

Letter coding: Alphabets in a word are replaced by other alphabets according to a specific rule to know its code. So the common rule should de detected first. Some examples are given below:

1) ‘ZYXW’ as coded as ‘ABCD’ then ‘STUV’ is coded as...........

Answer: Z – A, Y– B, X – C, W – D
V – E, U – F, T – G, S – H
Answer = HGFE
Rule= front alphabet= back alphabet.

2) ‘ bcd’ is coded as ‘def’ then ‘True’ is coded as..........

Answer: b – d (+2)
c – e (+2)
d – f (+2)
+2 letters are considered in this code.
True – Vtwg
Answer = Vtwg.

3) ‘ Hyderabad ’ is coded as ‘Ixedszcze’ then ‘Chennai’ is coded as..............

Answer: H – I (+1)
Y – X (1–)
D – E (1+)
E – D (1-)
R – S (1+)
A – Z (1–)
B – C (1+)
A – Z (1– )
D – E (1+)
Here if we observe alternatively the letter increasing and one letter decreasing.
Chennai =dgfmozj
Answer = dgfmozj

Number coding: In this each alphabets or words are assigned to the numeric values we should observe the given letters and the assigned values and use the same rule to find the value to of given code. Some examples are given below:

1)Apple is coded as 25563, Rung is coded as 7148. Then purple is coded as


PURPLE – 517563
Answer = 517563.

2)In a language A is coded as 1, B is coded as 2, ….. then FACE is coded as


Then FACE = 6135
Answer = 6135.

3)PUSH is coded as 1234, ROUGH is coded as 65274. Then SOUP is coded as


SOUP = 3521
Answer = 3521.

Substitution: In this section an object names are substituted with different object names. We should carefully trace the substituion and answer given question. Some examples are given below:

1)‘book’ is coded as ‘pencil’, ‘pencil’ is coded as ‘mirror’, ‘mirror is coded as ‘book’. Then what is useful to write on a paper?

Answer: Pencil is coded as mirror
Answer = mirror.

2)‘man is coded as ‘woman’, woman is coded as ‘girl’, ‘girl’ is coded as ‘boy’, ‘boy’ is coded as ‘worker’ then 6 years female is known as?

Answer: 6 years female = girl, but ‘girl’ is coded as ‘boy’.
Answer = boy.

3)‘Reds’ are ‘blues’, ‘blues’ are ‘whites’, ‘whites’ are ‘yellows’, ‘yellows’ are ‘oranges’, ‘oranges’ are ‘pinks’, then what is the colour of the sky?

Answer: Sky is blue, but blues are whites
Answer = white.

Exercise questions

1.In a certain code, COMPUTER is written as RFUVQNPC. How is MEDICINE written in the same code ?

Ans: Option d
The letters of the word are written in reverse order and expect the first and the last letter all other letters are
move one step forward

2.In a code language, A is written as B, B is written as C, C is written as D and so on, then how will SMART be written in that code language ?

Ans: Option c
The letters are coded by moving them 1 step forward.

3.In a certain code , RIPPLE is written as 613382 and LIFE is written as 8192. How is PILLER written in that code?

Ans: Option a:
Word : R I P P L E L I F E P I L L E R
Code : 6 1 3 3 8 2 8 1 9 2 3 1 8 8 2 6

4.In a certain code FLOWER is coded as 36 and SUNFLOWER is coded as 81, then how to code FOLLOWS?

a) 42 
d) 36
Ans: Option b
The word FLOWER has 6 letters . 62 is 36
The word SUNFLOWER has 9 letters. 92 is 81
Like FOLLOWS has 7 letters. So 72 is 49

5.In a certain code ,'il be pee' means 'roses are blue','sik hee' means 'red flowers' and 'pee mit hee' means 'flowers are vegetables', How is 'red' written in that code?

d)cannot be determined 
Ans: Option b
Code Sentence
Il be pee roses are blue
Sik hee red flowers
Pee mit hee flowers are vegetables
In II and III code ‘hee’ stands for ‘flowers’. So ‘sik’ stands for ‘red’

6.In a certain code language : ‘dugo hui mul zo’ stans for ‘work is very hard’ ‘hui dugo ba ki’ for ‘Bingo is very smart’; ‘nano mul dugo’ for ‘cake is hard’; and ‘mul ki gu’ for ‘smart and hard’ Which of the following word stand for Bingo ?

a) Jalu 
b) Dugo 
c) Ki 
d) Ba
Ans: Option d
Code Sentence
1.dugo hui mul zo work is very hard
2.hui dugo ba ki bingo is very smart
3.nano mul dugo cake is hard
4.mul ki gu smart and hard

From second code and its sentence neither ‘ba’ is repeated nor is ‘Bingo.

7.If rain is called water, water is called air, air is called cloud, cloud is called sky, sky is called sea, sea is called road, where do the aeroplanes fly ?

a) Water 
b) Road 
c) Sea 
d) Cloud
Ans: Option c
Aeroplanes fly in sky and as per given codes sky is sea

8.If Orange is called Lemon, Lemon is called Flower, Flower is called Fish, Fish is called Tail and Tail is called Pen, what is Rose ?

a) Pen 
b) Lemon 
c) Flower 
d) Fish
Ans: Option d
Rose is a flower and as per given codes flower is fish.

9.In a certain code language $#* means ‘Shirt is clean’, @ D# means ‘Clean and neat’ and @ ? means ‘neat boy’, then what is the code for ‘and’ in that language

a) # 
b) D 
c) @ 
d) Data inadequate 
Ans: Option b
Code sentence
$#* ‘Shirt is clean’,
@ D# ‘Clean and neat’
@ ? ‘neat boy’
Here # stands for clean and @ stands for neat. D stands for ‘and’

10.If A stands for +, B stands for -, C stands for x, what is the value of (10C4)(A) (4C4)B6 ?

a) 60 
b) 50 
c) 56 
d) 46
Ans: Option b
(10C4)(A) (4C4)B6 = (10 * 4) + (4*4) –6 = 50